Integrated laser arrays and support circuits

ABSTRACT

A two dimensional, surface-emitting array of semiconductor lasers. Lasers disposed on a semiconductor substrate emit light in a direction substantially parallel to the substrate surface into a high index material in which the lasers are embedded. Internal reflectors composed of a low index material, also embedded in the high index material, reflect the laser beams to the surface of the array. The indexes of the low index material and the high index material are chosen so that none of the light enters the internal reflector, and all light is reflected to the laser array surface.

This application is a continuation-in-part of U.S. Ser. No. 07/264,422filed Oct. 31, 1988, now abandoned.

BACKGROUND OF THE INVENTION

This invention generally relates to semiconductor laser arrays and moreparticularly, to a semiconductor laser array and a method of forming thelaser array where the laser beams emitted are directed perpendicular toor parallel along the surface of the chip by the use of a high indexmaterial.

Semiconductor laser arrays and laser lines have many potentialapplications including high power sources to pump solid state lasers anda variety of optoelectronic applications. Much of the current effort inlaser arrays is devoted to linear arrays of edge-emitting GaAs/AlGaAslasers, fabricated by growing AlGaAs alloy layers on a GaAs substrateand cleaving the GaAs substrate at both ends of the lasers to form thetwo laser mirrors of the resonant cavity. Several lasers or a row oflasers may be formed together by this process. Limited success has beenexperienced in fabricating two-dimensional arrays of lasers by stackingand joining several discrete linear laser arrays formed by such cleavingtechniques together.

Other efforts include building monolithic two-dimensional laser arrayswhich have been fabricated as a grid of semiconductor devices which emitlaser beams perpendicular to the surface of the chip. Prior art devicesin this category include arrays which use lasers with their resonantcavities normal to the wafer surface, arrays with chemically etched 45°mirrors or arrays utilizing a second order grating coupler. However, theefficiencies of most of these prior art lasers were too low to be ofpractical interest. A more promising technique is to use devices formedby coupling edge emitting laser diode with external mirrors formed byetching 45° parabolic or slant mirrored surfaces on the chip. Thistechnique is described in an article by T. H. Windorn and W. D. Goodhue,entitled "Monolithic GaAs/AlGaAs Diode Laser/Deflector Devices for LightEmission Normal to the Surface," Appl. Phys. Lett. 48 (24), 16 June1986.

There are, however, several problems with the prior art which limit thepower, size and manufacturability of two-dimensional laser arrays.

Forming the mirrors of the resonant cavity by cleaving is suitable forthe fabrication of a linear array of lasers. However, in a linear array,the narrow shape of the substrate formed by cleaving sharply limits thelocation and amount of support circuitry and wiring that can beintegrated in the laser substrate. Support circuitry such as lasercontrol logic, memory devices, decoders, input-output ports and powersupplies can only be accommodated on the two remaining sides of thelaser. Whether these support devices are most ideally placed adjacent tothe laser or at the periphery of the substrate, the cleaved mirrortechnique presents severe obstacles to the chip designer. Anotherproblem with the cleaving technique is that electrical testing of thedevices cannot be performed until the laser chips are mounted in theirpackages.

While limited success has been experienced in fabricating twodimensional arrays from a series of cleaved linear laser arrays, thesearrays share all of the same problems of the linear arrays and add somenew ones of their own. Discrete wires are used to interconnect thestacked laser arrays. The numerous external electrical connections raiseconsiderable reliability concerns when compared to the interconnectingmetallurgy used on an integrated chip. In addition, interference amongthe laser beams determines the light pattern of the laser array, and asthe interference pattern is in part determined by the position of thelasers, the positioning of the lasers within the array must be precise.It is quite difficult to form an array of stacked lasers, consequentlythe positioning of the laser elements within the array can varysignificantly from array to array.

A monolithic two dimensional laser array avoids some of the problemsinherent in cleaving the substrate to form laser mirrors allowinggreater freedom in locating support devices and greater precision in thepositioning of laser elements in the array. However, the 45° parabolicor slant mirrors used in the prior art are formed by depositing areflecting metal film on the slanting surface on the substrate. Mirrorreflection is not 100 percent efficient and particularly at some wavelengths of light, significant power is lost at the mirrored surface. Asa result, in addition to losing light output, the heat which must bedissipated by the chip is higher. One of the major problems limiting thesize of the laser array is that it becomes progressively more difficultto remove waste heat as the size of the array increases. It would beclearly advantageous to eliminate the power loss at the mirror surface.Other problems in using metallic mirror surfaces include potentialcorrosion concerns, and mechanical problems including difficulties ofattaching optical fibers to mirror reflectors mounted at a slopingangle.

Topology concerns play a significant factor in fabricating large laserarrays. Using current deposition methods, the laser can be significantlyhigher than the substrate on which it is situated. The side edges of thelasers present sharp topographical features to the overlyinginterconnecting metallurgy. To reduce yield and reliability problems, agradually sloping spacer can be included at the side edges of the laser.However, these sloping spacers use up chip area, reducing laser andcircuit packing density. All of these factors pose problems in achievingfunctional and reliable metalization connecting support circuit elementson the supporting substrate adjacent to the laser.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved laserarray on a semiconductor substrate which emits laser beams perpendicularto the surface of the substrate.

It is another object of the present invention to provide an improved twodimensional laser array with a smooth topological surface suitable forinterconnecting lasers and circuit elements.

It is another object of the present invention to transmit the light outof the laser array with minimal Fresnel and scattering losses.

It is another object of the present invention to integrate the improvedlaser array with one or more optical fibers.

It is yet another object of the present invention to reduce power lossat the mirror reflector.

These and other objects of the invention are accomplished by embeddingthe laser in a high index material, providing the high index material asthe light path connecting the laser and the surface of the chip, and touse an internal reflector having a slanted surface and composed of a lowindex material to produce the required amount of deflection of the laserbeam by total internal reflection so that the beam emerges from thesurface of the array with minimal loss of light.

In the preferred embodiment of the invention, four optical surfaces areformed at each laser element: two laser mirrors which define theresonant cavity, a 45° total internal reflector structure adjacent tothe output facet of the laser, and an optically flat surface at thearray surface above the internal reflector. The internal reflector ismuch more efficient than a mirrored surface since the high and low indexmaterials are chosen so that 100% of the beam is deflected at a 90°angle at the interface of the materials, no light is lost bytransmission through the low index material. The process of theinvention is designed to avoid damage to each optical surface assubsequent process steps are performed and optical surfaces are formed.

In an alternate embodiment of the invention, two 45° internal reflectorstructures are used, one at either facet of the laser as both facets aredesigned to emit a laser beam. Thus, in the alternative embodiment, twolaser beams are produced by each laser element, and five opticalsurfaces are formed at each element. By dividing the beam in two, agreater total power output by each laser element can be maintained.

The foregoing and other objects, features and advantages of the presentinvention will be made more apparent from the following description ofthe preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, illustrate one embodiment of the inventionand together with the description, serve to explain the principles ofthe invention.

FIG. 1 shows a cross sectional view of the laser, the substrate, andrelated reflecting surfaces.

FIG. 2 shows the relationship between the angles of incidence andrefraction of the laser beam at the interface of the high index materialand the internal reflector.

FIGS. 3A through 3H are sectional views, dimensionally exaggerated, ofthe chip showing process steps for the fabrication of the laser deviceshown in FIG. 1.

FIG. 4 shows a top view of a laser array built in accordance with thepresent invention.

FIG. 5 is a wiring diagram of a laser array and attendant supportingcircuitry.

FIG. 6 is a perspective view of an embodiment of the invention where thelight of the laser is first reflected parallel to the substrate surfacebefore being reflected to the surface of the laser array.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a cross section of an individual AlGaAs laser 20alongthe axis of the laser beam is shown. The laser 20 consists of aseries of very thin crystalline layers of AlGaAs grown epitaxially on aGaAs substrate 22. The total thickness of these layers is approximately3 um. The resonant cavity is formed by twin polished reflecting surfaces24 and 25. The reflecting surfaces 24 and 25 are capped by mirrors 26and 27, which may be a metallic layer, or may be a dielectric layer suchas an alumina or a silicon nitride layer deposited in a conformalthickness equal to one quarter or one half wave length of the laserlight generated by the laser 20. The choice of material at reflectingsurfaces 24 and 25 is dependent on the degree of reflectivity desired ateach interface. If ametallic layer is used the reflectivity isdetermined by the thickness of the layer. In the preferred embodiment,only one laser beam is produced byeach laser element 20. Thus, it isdesirable to have a highly reflecting surface at surface 24 and a highlytransmissive surface at output surface 25. Together with the slantedinternal reflector 28 which is formed out ofa low index material such asSiO₂, the laser 20 is embedded in a layerof high index material 32 suchas TiO₂ which is slightly thicker than the laser 20 itself. The surface34 of the high index material 32 is polished to provide an opticalsurface which has the additional benefit ofbeing a planar surface forinterconnecting metallurgy. The high index material 32 is capped by anantireflective coating 36, which promotes better optical couplingbetween the laser 20 and the optical fiber 40 and reduces Fresnel lossesout of the chip.

When a small voltage is applied to the laser 20 via the electricalcontact 42, electric current flows and carriers, electrons and holes,are injectedinto the active region of the laser 20. Upon recombining,the carriers generate light; optical feedback in a direction parallel tothe surface ofthe substrate 22 is produced by the reflecting surfaces 24and 25. Light isemitted from the surface 25 into the high index material32. The angle and indexes of refraction of the internal reflector 30 andhigh index materialare chosen to deflect the light perpendicularly sothat the laser beam emerges from the chip surface 38. A waveguide oroptical fiber 40 may alsobe attached to the surface 38 of theantireflective coating 36, or to the high index material 32 if theantireflective coating 36 is omitted, for each laser 20 or to combinethe light of the entire array.

In an alternative embodiment, a second slanted internal reflector likereflector 28 is placed opposite surface 24. Both surface 24 and 25 aretransmissive rather than reflective surfaces, resulting in two laserbeamsbeing produced by each laser 20. Both beams of light would beemitted normal to the chip surface 38.

One of the key features of a laser array built according to the presentinvention is the use of the high index material 32 in combination withtheslanted surface of the internal reflector 30 which is formed from amaterial with a substantially lower index of refraction. As thisrelationship is critical for implementing the invention, the followingdiscussion is provided:

The index of refraction of a material is defined as the ratio of speedof light in air to the speed of light in the material. Light will travelslower in a high index material than in a low index material. Because ofthe difference in speed, the direction of a light wave changes when itcrosses the interface between materials of different indexes ofrefraction. Referring to FIG. 2, the angle of incidence abN and theangle of refraction nbc are related to the indexes of refraction bySnell's law which states: ##EQU1##

Where n₁ equals the index of refraction of the first higher indexmaterial, n₂ the index of refraction for the second lower indexmaterial, sin θ₁ equals the angle of incidence (abN) and sin θ₂ equalsthe angle of refraction nbc of the light after it strikes the interface.If light traveling in a material strikes an interface with a secondmaterial of lower index and at an angle of incidence equal to or greaterthan the "critical angle", none of the lightwill penetrate across theinterface to enter the second material. In other words, the criticalangle is that angle of incidence for which of the angle of refraction is90°. At angles greater than the "critical angle", all of the light willbe reflected back into the first material atan angle equal to the angleof incidence. In FIG. 2, the laser beam would travel in the high indexmaterial along the path ab, hit the interface between the high index andlow index material at point b, and resume its passage in the high indexmaterial along path bc".

In the case of the preferred embodiment as illustrated in FIG. 1, theangleof incidence is 45°, and therefore the critical angle must be 45°or less to achieve total internal reflection. Substituting these valuesinto Snell's Law yields: ##EQU2##so that the high index material 32 musthave an index of refraction equal to or greater than 1.414 times theindex of refraction of the material which makes up the internalreflector 28. For example, if SiO₂, whichhas an index of refraction of1.46, were used for the internal reflector 28, then the high indexmaterial must have an index of refraction greater than 2.06. Other lowindex transparent materials such as NaF, LiF and MgF have indexes ofrefraction in the range 1.32 to 1.38. Using these materials to build theinternal reflector 28, the high index material can have an index as lowas 1.9. In addition, if the particular application can tolerate laserbeams which do not emerge exactly normal from the surface of the chip,but at some lesser angle, the slant on the internal reflector can beless than 45°. Less of a difference would be required between theindexes of refraction of the low and high index material if the internalreflector 28 were slanted at 30° from the substrate rather than 45°. Onthe other hand, where a curved surface 30 is used in the internalreflector 28, to focus the laser beam, greater differences between theindexes of refraction of the high and low index materials would benecessary since the light striking at the upper half of a curved surfacewould strike at an interface with an angle of incidence less than 45degrees.

The process of fabricating the present invention will be describedhereinbelow with particular reference to the use of AlGaAs on a GaAssubstrate to form an individual laser device is shown in FIGS. 3Athrough 3H. It should be understood that other solid state laserstructures and materials, such as the InGaAlP/GaAs and InPGaAs/InPsystems, can also be used in accordance with the present invention.While the invention is described in terms of a preferred embodiment, itis not limited to any particular structure, combination of materials,set of thicknesses, or sequence of layers.

Referring to FIG. 3A, epitaxial AlGaAs layers which form the laser 20are deposited on the GaAs substrate 22. In one embodiment, these layersinclude a first layer of Al₀.4 Ga₀.6 As with a thickness of 3.3 microns,an intermediate layer of Al₀.1 Ga₀.9 As with a thickness of 0.15microns, and an upper layer of Al₀.4 Ga₀.0 As with a thickness of 1.3microns. Those skilled in the art would understandthat the thickness ofthe AlGaAs layers and the mole fraction of Al, Ga andAs in those layerscan be varied to produce a particular desired wavelengthof light. In theAlGaAs system, the range of achievable wavelengths is between 680 and860 nm. Suitable methods for the formation of the AlGaAs layers includeliquid phase epitaxy, vapor phase epitaxy, and molecular beam epitaxy. Alayer of photoresist is applied, exposed and developed to leave aphotoresist mask 23 over the laser area.

Along with the laser 20, other circuit elements, such as transistors,diodes, capacitors and resistors (not shown), may also be formed in thesubstrate 22. Because of the monolithic nature of the laser array of thepresent invention, other circuit elements may be located on all foursidesof the structures shown according to the preferences of the circuitdesigner. Integrating these support devices may add substantially toprocess complexity necessary to fabricate the overall monolithic laserarray. However, these devices are outside the boundaries of the presentinvention.

As shown in FIG. 3B, the laser 20 is formed using a recently developedprocess, Reactive Ion Beam Assisted Etching (RIBAE), which is alsocalled Chemical Assisted Ion Beam Etching in the prior art. RIBAE isused to remove the AlGaAs layers stopping at the GaAs surface. AfterRIBAE, the remaining photoresist is stripped; the result is thestructure seen in FIG. 3B, which shows one of the laser devices 20 inthe laser array.

In RIBAE, the substrate is placed in the evacuated chamber of ReactionIon Beam Etcher such as the Varian Re-480, an argon ion beam is directedto the substrate surface and a reactive gas is flowed over thesubstrate. Typically, chlorine (Cl₂) is used as the reactive gas to etchAlGaAs.Typical process parameters would be 500 ev argon ions atapproximately 0.40mA/cm² current density and, 14 sccm Cl₂ flowing overthe substrate. The RIBAE process forms mirror surfaces 24 and 25 nearlyas smooth as cleaved surfaces. Other processes which chemically ormechanically form an optically smooth surface may also be used to formthelaser 20, including selective chemical etching and mass transport.

Referring to FIG. 3C, the laser missors 26 and 27 are formed on thesmooth optical surfaces 24 and 25 of the laser. Chemical vapordeposition (CVD) may be used for a dielectric material such as Si₃ N₄ orAl₂O₃. While other methods of deposition may be possible, the CVDprocessis preferred as it provides a very uniform and controlled layerof deposition material. Alternatively, partial or full metal reflectors,suchas aluminum, gold or platinum, may also be deposited usingevaporation techniques or CVD processes using an organometallic vapor asa source. Thematerial and its thickness may be selected to enhancereflection or to enhance transmission. If output from only one end ofthe laser 20 is beingused as in the preferred embodiment, anantireflective coating such as a quarter wave plate of dielectricmaterial 27 is formed at surface 25 and areflective coating 26 such asgold is evaporated on surface 24. If the output from both sides is used,partially reflective coatings 26 and 27 are applied to both surfaces 24and 25. In the process used for illustrative purpose, it is importantthat the materials used for laser coatings 26 and 27 be impervious to HFsince HF will be used in a subsequent processing step. However, it ispossible to use other etchants or etching techniques to fabricate alaser array according to the present invention.

As shown in FIG. 3D, a film 28 of low index material such as SiO₂, isthen deposited by chemical vapor deposition. The film 28 should beapproximately equal in thickness to the laser 20. A 45° angle structureis then formed in two masking steps. In the first masking step shown inFIG. 3D, photoresist is applied and developed away all areas fromotherthan where the internal reflector 28 is to be located formingphotoresist mask 29. Next, the bulk of the SiO₂ is etched away from thelaser using HF, a wet chemical etch process while the SiO₂ which willform the internal reflector 28 is protected by photoresist mask 29.

As shown in FIG. 3E, photoresist mask 29 is removed and the secondmasking step is performed: resist is applied, developed and exposed toleave photoresist pattern 31 so that the laser mirrors 26 and 27 areprotected. The wafer is tilted with respect to the ion beam to achievethe 45°angle of the internal reflector and RIBAE as the etching process.In an alternate embodiment, the wafer tilt may also be adjusted duringthe RIBAEprocess to produce a curved surface which will bring the laserbeam to a focus. The remaining resist is stripped and resultingstructure is shown in FIG. 3F.

As shown in FIG. 3G, a high index transparent material 32, such as TiO₂,Ta₂ O₅, Si₃ N₅, ZnS, or SiC is deposited using chemical vapordeposition. As shown in FIG. 3G, the layer 32 conforms to the topologyof the existing structures. The layer 32 of high index materialdeposited must be significantly thicker than the laser and the low index45° angle structure to allow for subsequent planarization. The highindex material 32 is ideally thick enough to accommodate the height ofany support circuitry (not shown) which might bepresent on the substrate22.

As shown in FIG. 3H, the wafer is mechanically orchemically-mechanically polished to eliminate all topological featuresleaving an optically flat surface 34. RIBAE or other ion beam millingtechniques can produce an optically flat surface, but require moreexpensive tooling and greater process time. A quarter waveanti-reflective plate 36 of a low index material such as Al₂ O₃ or MgF₂can be applied to the polished surface to reduce Fresnel power loss. Thelow index material may be deposited by evaporation, chemical vapordeposition, or other processes. The material used for the quarter waveplate 36 should be intermediate between that of the high index material32 and the air. If anoptical fiber 40 is used, it should be intermediatebetween the high index material 32 and the optical fiber 40.

As shown in FIG. 1, a metal contact 42 may be attached to the surface ofthe chip to connect the lasers and other circuit elements. First, a viaisetched through the materials covering the laser 20. Then, the metalcontact42 is formed on the via by well known lift-off or metal etchprocesses. Also as shown in FIG. 1, optical fibers 40 may be attached tothe surface of the laser chip.

The indices of refraction of typical high index materials are presentedin the table below:

    ______________________________________                                        Material    Index of Refraction                                               ______________________________________                                        Si.sub.3 N.sub.5                                                                          1.9-2.1                                                           Ta.sub.2 O.sub.5                                                                          2.1-2.3                                                           ZnS         2.3-2.4                                                           TiO.sub.2   2.3-2.6                                                           ______________________________________                                    

The internal reflector 28 may be formed out of SiO₂, which has an indexof refraction of 1.46, significantly lower than the above listedindices. For example, the critical angle for a TiO₂ -SiO₂ interface is39°; thus light will be totally reflected from the 45° SiO₂ surface.Small variation in the angle of the low index surface 30 may be used,including providing curvature to bring the beam to a focus. As statedabove, a variety of films can be used to form the laser mirrors 26 and27, depending on the desired amount of reflectionand transmission. Asufficiently thick layer of metal provides a highly reflective lasermirror. Another possible choice for a highly reflective mirror would bea dielectric film with an appropriate index of refraction.Highlytransmissive films would include high index materials such as thoselisted above. Since HF does not attack GaAs, when it is used to form theinternal reflector 28, see FIG. 3, no laser mirrors 26 and 27 arerequiredif transmission from the laser 20 is to be maximized. Partiallyreflective materials would include a thin metal film, althoughabsorption losses makeit a less desirable choice than a thin dielectricfilm of a thickness and index of refraction chosen for maximuminterference effects.

FIG. 4 shows a top view of the laser array. Each laser 20 is shown witha single internal reflector 28. Transparent layers of the high indexmaterial 32 and the antireflective layer 36 cover the entire array. Asshown in FIG. 3, all lasers 20 in each row are wired in parallel byinterconnecting lines 50 so that all the lasers 20 in a particular rowwill be either "on" or "off". If independent control of each laser isdesired, each laser 20 could be wired individually as the metal contacts42 can contact the top surface of the laser 20 at any point on itslength.

It is also possible to include support circuitry in the laser array.FIG. 5is a wiring diagram of laser array in which each individual laser20 is wired to a corresponding transistor 60. When both the row 62 andthe column 64 is powered, the transistor 60 switches on powering thelaser 20.The laser array also has standard elements such as row andcolumn decoders 66 and 68, I/Os 70 and connections to power supply 72.

A perspective view of yet another embodiment of the present invention isshown in FIG. 6. An internal reflector 28' is fabricated so that its 45°slanted surface is orthogonal to the surface of the substrate 22 and thelaser beam travels in the high index material 32 parallel to the surfaceof the substrate 22. A second internal reflector 28" is placedin thelaser beam path to reflect light to the laser array surface 38 at thedesired point. This embodiment of the invention is useful foroptoelectronic chips in which light is processed on the laser arraysurface.

While several embodiments of the invention, together with modificationsthereof, have been described in detail herein and illustrated in theaccompanying drawings, it will be evident that various furthermodifications are possible without departing from the scope of theinvention. For example, although all illustrative embodiments portrayedsemiconductor lasers, semiconductor LEDs could also be used inaccordance with the present invention. Semiconductor LEDs are similar incomparison to semiconductor lasers, the main differences being in thelack of a resonating chamber and a less exacting criteria in the dopingof the various semiconductor layers in an LED. In addition,photodetectors can beintegrated into the array to receive the light fromthe laser deflected along the surface of the semiconductor substrate inthe embodiment shown in FIG. 6, replacing the second internal reflector28" for a photodetector.

What is claimed is:
 1. A semiconductor laser element comprising:asemiconductor laser formed by sequential epitaxial layers ofsemiconductor material disposed on a semiconductor substrate so thatlight produced by said semiconductor laser is emitted in a directionsubstantially parallel to said semiconductor substrate; an internalreflector composed of a low index material having a slanted surface,said internal reflector disposed on said semiconductor substrateadjacent to said semiconductor laser and positioned to deflect lightemitted from said laser on said slanted surface; a high index materialdisposed on and embedding both said semiconductor laser and saidinternal reflector so that light emitted from said semiconductor laserenters said high index material before striking said slanted surface;wherein the indexes of refraction of said low index and said high indexmaterial are chosen so that all of the light emitted by said laserstriking said slanted surface of said internal reflector is deflectedback into said high index material at an angle equal to the angle ofincidence.
 2. The semiconductor laser element as recited in claim 1wherein said slanting surface is at a 45 degree angle from said surfaceof said semiconductor substrate and said light is emitted substantiallyperpendicular from the surface of said semiconductor substrate.
 3. Thesemiconductor laser element as recited in claim 1 which furthercomprises an antireflective layer of material deposited on at least oneend of said semiconductor laser of a thickness equal to a halfwavelength of said light emitted from said laser to form an emittinglaser mirror of the resonant cavity of said laser.
 4. The semiconductorlaser element as recited in claim 1 which further comprises anantireflective layer disposed on said high index material to reduceFresnel losses from said semiconductor laser element.
 5. Thesemiconductor laser element as recited in claim 2 wherein said slantingsurface is curved to focus said light emitted from said laser element.6. A semiconductor laser array comprising:a plurality of semiconductorlasers formed by sequential epitaxial layers of semiconductor materialdisposed on a semiconductor substrate so that light produced by each ofsaid plurality of semiconductor lasers is emitted in a directionsubstantially parallel to said semiconductor substrate; a plurality ofinternal reflectors composed of a low index material, each of saidplurality of internal reflectors having a slanted surface, each of saidinternal reflectors corresponding to a respective semiconductor laserand disposed on said semiconductor substrate adjacent to said respectivesemiconductor laser positioned to deflect light emitted from saidrespective laser on said slanted surface; a high index material disposedon and embedding both said plurality of said semiconductor lasers andsaid plurality of said internal reflectors so that light emitted fromeach of said plurality of semiconductor lasers enters said high indexmaterial before striking said slanted surface; wherein the indexes ofrefraction of said low index and said high index material are chosen sothat all of the light striking said slanted surfaces of each of saidplurality of internal reflectors is deflected back into said high indexmaterial at an angle equal to the angle of incidence.
 7. Thesemiconductor laser array as recited in claim 6 wherein said slantingsurfaces are at a 45 degree angle from said surface of saidsemiconductor substrate and said light is emitted substantiallyperpendicular from the surface of said semiconductor array.
 8. Thesemiconductor laser array as recited in claim 6 which further comprisesa conformal layer of material deposited on at least one end of saidplurality of semiconductor lasers of a thickness equal to a halfwavelength of said light emitted from said semiconductor lasers to formlaser mirrors of the resonant cavities of said semiconductor lasers. 9.The semiconductor laser array as recited in claim 6 which furthercomprises an antireflective layer disposed on said high index materialto reduce Fresnel losses from said semiconductor laser array.
 10. Thesemiconductor laser array as recited in claim 7 wherein said slantingsurfaces are curved to focus said light emitted from said plurality ofsemiconductor lasers.
 11. A semiconductor laser element comprising:asemiconductor laser formed by sequential epitaxial layers ofsemiconductor material disposed on a semiconductor substrate so thatlight produced by said semiconductor laser is emitted in a directionsubstantially parallel to said semiconductor substrate; two internalreflectors composed of a low index material each having a slantedsurface, said internal reflectors disposed on said semiconductorsubstrate at either end of and adjacent to said semiconductor laser andpositioned to deflect light emitted from said laser on said slantedsurfaces; a high index material disposed on and embedding both saidsemiconductor laser and said internal reflectors so that light emittedfrom said semiconductor laser enters said high index material beforestriking said slanted surface; wherein the indexes of refraction of saidlow index and said high index material are chosen so that all of thelight emitted by said laser striking each said slanted surface of saidinternal reflectors is deflected back into said high index material atan angle equal to the angle of incidence.
 12. The semiconductor laserelement as recited in claim 11 wherein said slanting surfaces are at a45 degree angle from said surface of said semiconductor substrate andsaid light is emitted substantially perpendicular from the surface ofsaid semiconductor substrate.
 13. The semiconductor laser element asrecited in claim 11 which further comprises an antireflective layer ofmaterial deposited on at least one end of said semiconductor laser of athickness equal to a half wavelength of said light emitted from saidlaser to form an emitting laser mirror of the resonant cavity of saidlaser.
 14. The semiconductor laser element as recited in claim 11 whichfurther comprises an antireflective layer disposed on said high indexmaterial to reduce Fresnel losses from said semiconductor laser element.15. The semiconductor laser element as recited in claim 12 wherein saidslanting surface is curved to focus said light emitted from said laserelement.
 16. The semiconductor laser element as recited in claim 1,wherein said slanting surface is at a 90° angle from said surface ofsaid semiconductor substrate and said reflected light is directedsubstantially parallel along the surface of said semiconductorsubstrate.
 17. The semiconductor laser element as recited in claim 16wherein a photodetector disposed on said semiconductor substratereceives said reflected light from said slanting surface of saidinternal reflector.
 18. The semiconductor laser array as recited inclaim 1, wherein said slanting surfaces are at 90° angles from saidsurface of said semiconductor substrate and said reflected light isdirected substantially parallel along the surface of said semiconductorsubstrate.
 19. The semiconductor laser array as recited in claim 18wherein photodetectors disposed on said semiconductor substrate receivesaid reflected light from said slanting surfaces of said internalreflectors.
 20. A semiconductor light emitting element comprising:asemiconductor light emitting element formed by sequential layers ofsemiconductor material disposed on a semiconductor substrate so thatlight produced by said semiconductor light emitting element is emittedin a direction substantially parallel to said semiconductor substrate;an internal reflector composed of a low index material having a slantedsurface, said internal reflector disposed on said semiconductorsubstrate adjacent to said semiconductor light emitting element andpositioned to deflect light emitted from said light emitting element onsaid slanted surface; a high index material disposed on and embeddingboth said semiconductor light emitting element and said internalreflector so that light emitted from said semiconductor light emittingelement enters said high index material before striking said slantedsurface; wherein the indexes of refraction of said low index and saidhigh index material are chosen so that all of the light emitted by saidlight emitting element striking said slanted surface of said internalreflector is deflected back into said high index material at an angleequal to the angle of incidence.
 21. The semiconductor light emittingelement as recited in claim 20 wherein said slanting surface is at a 45degree angle from said surface of said semiconductor substrate and saidlight is emitted substantially perpendicular from the surface of saidsemiconductor substrate.
 22. The semiconductor light emitting element asrecited in claim 16 which further comprises an antireflective layerdisposed on said high index material to reduce Fresnel losses.
 23. Thesemiconductor light emitting element as recited in claim 20 wherein saidslanting surface is curved to focus said light emitted from said lightemitting element.
 24. The semiconductor light emitting element asrecited in claim 20 which further comprises a second internal reflectordisposed on said semiconductor substrate adjacent to said semiconductorlight element and positioned to deflect light emitted from saidsemiconductor light element on said slanted surface.
 25. Thesemiconductor light emitting element as recited in claim 20 wherein saidslanting surface is at a 90 degree angle from said surface of saidsemiconductor substrate and said reflected light is directedsubstantially parallel along the surface of said semiconductorsubstrate.
 26. The semiconductor light emitting element as recited inclaim 25 wherein a photodetector disposed on said semiconductorsubstrate receives said reflected light from said slanting surface ofsaid internal reflector.